Malignant bowel obstruction


Case presentation

A 53-year-old white man with recently diagnosed poorly differentiated gastric adenocarcinoma containing signet ring cell features was admitted with a 1-day history of severe left lower quadrant abdominal pain radiating throughout the abdomen, associated nausea, and 2 days without bowel movements or flatus. Vital signs were unremarkable, and physical exam was notable for a distended, tympanitic, markedly tender abdomen with hyperactive bowel sounds. A complete blood count, basic metabolic panel, and liver function tests were unremarkable. An abdominal radiograph revealed multiple dilated loops of small bowel and a “string of pearls” appearance in the left mid-abdomen with multiple air-fluid levels at differing heights. A CT scan showed a moderate- to high-grade small-bowel obstruction with a transition point in the pelvis approximately 25 cm proximal to the ileocecal valve, with evidence of omental metastases.

Supportive care was initiated with placement of a nasogastric tube connected to low-intermittent wall suctioning, intravenous hydration, pain control, antiemetics, and octreotide. General surgery was consulted, but due to extensive metastatic disease, including suspected peritoneal carcinomatosis on CT scan, the patient was felt to be a poor surgical candidate, and conservative management was continued. Total parenteral nutrition was started, and dexamethasone was added.

Oncology was consulted, and the patient underwent inpatient chemotherapy with FOLFOX (leucovorin, oxaliplatin, and 5-fluorouracil). After interventional radiology was consulted, the patient underwent venting gastrostomy tube placement for palliation. When pain and nausea had finally improved, he was transitioned to full liquid diet and maintained on total parenteral nutrition after discharge. He was discharged on oral metoclopramide and a course of dexamethasone.

Background

Malignant bowel obstruction (MBO) is a common complication, particularly in patients with gastrointestinal or gynecological cancer. MBO can be defined as luminal narrowing of small or large bowel with clinical evidence of bowel obstruction in the setting of metastatic intra-abdominal cancer. Colorectal and ovarian cancers are the most common intra-abdominal cancers associated with malignant bowel obstruction, whereas breast cancer and melanoma are the most common extra-abdominal causes.

Patients describe gradual worsening of abdominal pain and progressively worsening nausea/vomiting as the disease progresses to complete bowel obstruction. Patients may also experience overflow diarrhea as a result of bacterial overgrowth secondary to the blockage of fecal material.

Classification

The pathophysiology of bowel obstruction is related to mechanical obstruction (extrinsic or intrinsic occlusion by tumor) or functional obstruction/adynamic ileus (caused by tumor infiltrating the bowel wall, nerves, and plexus). MBO can be classified by partial versus total obstruction and proximal versus distal bowel obstruction.

Symptoms and management of proximal versus distal bowel obstruction differ significantly (1, 2). For example, gastric or proximal small-bowel obstruction may present with bilious vomiting; postprandial periumbilical, intermittent abdominal pain; and intolerance to oral intake, but no abdominal distention. Malignant small-bowel obstruction most often occurs at the level of the duodenum, as a result of extrinsic compression or direct invasion by the tumor. Pancreatic adenocarcinoma, cholangiocarcinoma, and gallbladder carcinoma are the most common tumors to cause duodenal obstruction. In contrast, distal small-bowel or large-bowel obstruction may present with malodorous emesis; localized deep, visceral pain, occurring at longer intervals; and abdominal distention.

Diagnosis

Although the diagnosis of malignant bowel obstruction can often be established based on history and physical exam, obstruction needs to be confirmed with imaging studies (1, 3). Radiologic imaging begins with abdominal X-ray and CT. Once an obstruction site is identified, direct visualization by endoscopy might be helpful for evaluating and treating the obstruction. The abdominal X-ray is used to look for dilated loops of bowel, air fluid levels, or both. The abdominal CT is useful in making the diagnosis of bowel obstruction, evaluating for complications, and staging and choosing surgical or endoscopic intervention. An abdominal CT has a sensitivity of 93%, a specificity of 100%, and an accuracy of 94% in determining the cause of bowel obstruction.

Treatment

Initial assessment of the patient should include determination of whether an acute abdominal emergency requires surgery. Surgical treatment options for MBO include debulking, diverting colostomy, intestinal bypass, and resection. In general, surgical candidacy is based on performance status, the extent of malignancy, and prognosis. Resection should be considered in patients with good performance status and localized disease (3). In advanced cancer, the benefit of surgical intervention is less clear and should be individualized to each patient. Poor prognostic indicators include age greater than 63 years, malnutrition, hypoalbuminemia, ascites/peritoneal carcinomatosis, metastatic effusions, multiple sites of obstruction, prior radiation to abdomen, prolonged bowel passage time, and short diagnosis to obstruction time (2, 3). Perioperative mortality ranges from 20% to 40%, with complication rates as high as 90% in advanced cancer patients (2).

Nasogastric tubes are often placed in initial treatment for decompression if symptom relief does not occur with medications. However, nasogastric tubes are not a long-term treatment option and can contribute to patient discomfort. For patients with chronic or recurrent obstructions who are not surgical candidates but benefit symptomatically from nasogastric tube decompression and have ongoing high gastric output, a venting percutaneous gastrostomy (G) tube may be an alternative palliative option. While symptomatic relief with a G tube may be achieved in 83% to 93% of patients, there is insufficient evidence to show that tube placement improves nutritional status or quality of life (2). G tubes are usually avoided in patients with portal hypertension, large-volume ascites, and high bleeding risk.

Placement of self-expanding metallic stents (SEMS) offers palliation to nonsurgical candidates with a single point of obstruction at the gastric outlet or proximal small bowel. These stents can be placed endoscopically by gastroenterologists or by interventional radiologists. SEMS may be a good option for patients with a single site of proximal obstruction and intermediate life expectancy. Successful palliation of symptoms with duodenal stent placement has been reported to be as high as 90% (3, 4, 5). Covered SEMS have been shown to maintain patency longer but are not available in the United States (2). Complications include perforation (1.2%), stent migration (5%), and stent obstruction (18%) (5). There are limited data comparing stenting to surgical bypass.

Metal stents placed for malignant colorectal obstruction also have a high palliative success rate, with improvement in symptoms in about 75% of patients (3, 5). Complications are similar to those with upper gastrointestinal obstruction stenting and include perforation (4.5%), stent migration (11%), and reobstruction (12%) (5). Technical success is less likely with proximal colonic obstruction than distal obstruction, and obstructions related to extrinsic compression than intraluminal obstruction (3).

Medications

MBO is a negative indicator of a patient's prognosis, with an average survival rate of 3 to 8 months in patients who undergo surgery and 4 to 5 weeks in inoperable cases (5). Because most patients with MBO are not surgical candidates, medical therapy and palliation of symptoms remain the mainstay of treatment. Spontaneous resolution of obstruction in inoperable MBO with nasogastric decompression and medical therapy has been reported to occur in 30% of patients (5). Intravenous hydration and electrolyte repletion are critical in the acute stages of management. A multifaceted approach to symptom management includes the use of parenteral opioids, antiemetics, antispasmodics, and antisecretory agents.

Opioids can be administered via intravenous, subcutaneous, or transdermal routes to avoid exacerbating nausea with oral administration. Because many patients are tolerant to opioids from previous prescriptions for chronic cancer pain, dose should be titrated to effect. There are limited data comparing efficacy of different opioids, though fentanyl may have less constipating effect than the others (5).

Antiemetics are cornerstones of MBO treatment. The Table lists the medication options. In general, combination therapy with different mechanisms is more efficacious than single-agent therapy. While metoclopramide is favored over other antiemetics in patients with functional obstruction, it should be avoided in complete bowel obstruction or if it seems to worsen abdominal pain or nausea (3, 5). Other antiemetics that can be used are neuroleptics (haloperidol, prochlorperazine, chlorpromazine) and/or antihistaminic drugs. Antagonists of the 5-HT3 receptors (ondansetron or granisetron) are another option, though they may have more of a constipating effect than the other drug classes (5).

Anticholinergic agents such as scopolamine and glycopyrrolate can alleviate symptoms (by reducing gastrointestinal fluid secretions and cramping related to peristalsis), but side effects may be dose-limiting. Evidence supports the use of a somatostatin analogue octreotide (Sandostatin) to decrease gastrointestinal secretions and increase water/electrolyte absorption. This medication is usually well tolerated. Antihistamines and proton-pump inhibitors can be used as adjunctive therapy as well.

Corticosteroids are recommended for their bimodal benefit of relieving nausea and decreasing tumor-related inflammation and edema. Dexamethasone may even reduce bowel obstruction and lead to spontaneous resolution in MBO related to advanced gastrointestinal and ovarian cancer (5).

Nutrition

Enteral nutrition is usually withheld in the acute stages while treatment focuses on symptom relief. In some cases, percutaneous gastrostomy tube placement will not only help improve symptoms but also provide a route of nutrition in patients who can tolerate it. In surgical candidates, total parenteral nutrition (TPN) can be used as a bridge to optimize status perioperatively.

The role of TPN in patients with advanced cancer and inoperable MBO who are not able to tolerate enteral feeding is more controversial. This form of nutrition carries its own risks, which should be weighed against the patient's underlying condition and goals of care. Routine use of TPN in nonsurgical patients with advanced cancer is not recommended (5).

Summary

MBO represents an advanced stage of cancer and can signal the transition towards palliative treatment for many patients. The decision to pursue medical versus surgical treatment hinges on a variety of factors, including a patient's general health status and the extent of metastasis. The role of the hospitalist in MBO includes managing symptoms with medications and coordinating gastroenterology, surgery, interventional radiology, and oncology consultations. Initiation of discussions about goals of care, focused on nutrition and code status, is also appropriate and can guide transition of care decisions at discharge. The approach to treatment of MBO should be individualized to each patient.

Back to the case

Five weeks after discharge, the patient was readmitted with recurrent partial small bowel obstruction associated with gastrostomy tube clogging. The gastrostomy tube was flushed with resolution of symptoms and he was discharged home the next day. Two weeks after this admission, he returned with uncontrolled symptoms from bowel obstruction. Goals of care were readdressed, and the patient was discharged. He died 2 weeks later.